Question

Which of the following are true about sharks?
i. Their body fluids is isosmotic to external environment.
ii. They are osmoconformers.
iii. They control their internal environment independent of external environment.
iv. They are osmoregulators.

• A. i and ii only
• B. ii and iii only
• C. iii and iv only
• D. i and iii only

Hint:

Sharks = special osmoconformers (use urea to match seawater osmolarity).

Answer 1

The Correct Option is A

Concept:
Sharks are marine cartilaginous fishes that maintain osmotic balance differently from most marine organisms.

Step 1: Understand osmotic condition in sharks. Sharks maintain high levels of urea and TMAO in their body fluids, making them:
• Nearly isosmotic with seawater Thus, statement (i) is correct.

Step 2: Classify sharks. Since their internal osmotic concentration matches the environment, they behave as:
• Osmoconformers Thus, statement (ii) is correct.

Step 3: Evaluate remaining statements.
• (iii) Independent regulation → Characteristic of osmoregulators $\times$
• (iv) Osmoregulators → Not true for sharks $\times$

Step 4: Conclusion. \[ \text{i and ii are correct} \]